Enhanced bulk and high strength paper

ABSTRACT

Disclosed herein are systems and methods for attaching particulate additives to a population of cellulose fibers dispersed in an aqueous solution. The cellulose fibers are treated with an activator that forms complexes with them. The particulate additive is attached to a tether that is capable of interacting with the activator, thereby forming a tether-bearing particulate additive. The tether-bearing particulate additive can be added to the activated suspension of cellulose fibers. The resulting interaction between the tether and the activator forms durable complexes that attach the particulate additive to the cellulose fibers. Using these systems and methods, useful additives like starches can be attached to cellulose fibers, imparting advantageous properties such as increased strength to paper products formed thereby. These systems and methods are particularly useful for papermaking involving virgin pulp fibers, recycled fibers, or any combination thereof.

RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/US2013/076653, which designated the United States and was filed onDec. 19, 2013, published in English, which claims the benefit of U.S.Provisional Application Ser. No. 61/745,725, filed on Dec. 24, 2012 andU.S. Provisional Application Ser. No. 61/774,295 filed Mar. 7, 2013. Theentire contents of the above applications are incorporated by referenceherein.

FIELD OF THE APPLICATION

This application relates generally to making paper products.

BACKGROUND

High bulk is desirable in many paper and paperboard applications. Highbulk is beneficial when same or higher thickness can be achieved byusing the same amount of pulp (same basis weight). This is usefulparticularly in packaging applications where the stiffness of thepackaging board is directly proportional to the cube of the thickness ofthe board. Thus doubling of the bulk or thickness of the board at sameweight would increase the stiffness by a factor of eight. Manyapproaches have been used in the past towards achieveing high bulk. Useof debonding molecules that decrease the hydrogen bonding between fibersincrease bulk, as does the use of expandable particles. Debonders makethe paper weak, however, while expandable particles are expensive andfragile.

Traditionally, the fibers that are used in paper making are refined toincrease fiber-fiber contact, thereby increasing the strength of thepaper. This is done particularly when softwood (long fibers) andhardwood (stiff short fibers) are mixed to produce paper or paperboard.Hardwood is cheaper than softwood and usually is the predominant fiberin paper because of price and density. The somewhat cylindrical softwoodfibers are often refined (i.e., subjected to high shear) to produce flatribbon-like fibers that have fibrillated surfaces to improve interfibercontacts and bonding among themselves and with the shorter hardwoodfibers. Refined fibers also have improved surface properties that allowfor a smoother surfaced with decreased pore size. Refining also reducesthe bulk of a paper matrix by turning a round reed-like fiber into aflat, ribbon-like structure. These flat fibers attach well to otherfibers, yielding dense and strong sheets at the expense of bulk. Ifunrefined fibers are used in an effort to produce a bulkier paperproduct, the resulting sheet can be weak and even unusable.

High strength is desirable in many paper and paperboard applications,however, and there are many ways to achieve it. One way to achieve thisis by manufacturing dense, high-caliper sheets or boards. This requiresthe use of large amounts of expensive pulp, and produces a heavyproduct. Another method of creating high strength in paper products isto add starch as sizing.

In one approach, the sizing process uses cooked starch solutions toimpart stiffness or strength to the paper. In the sizing process, thewet web is first dried to a pre-set moisture content and/or is re-wet toachieve uniform moisture content throughout; then the material is fedinto a size press where a high loading of gelatinized starch is appliedto the paper surface; then the material is dried again. This processyields a strong paper, but involves a number of downstream processesthat can be inefficient. Inefficiencies result from the number of stepsinvolved in preparing the substrate, cooking the starch and applying itto form the finished product. A considerable amount of energy isrequired for these steps, which adds to the costs of the process.

In some instances, gelatinized starch can be added to the wet end of thepapermaking process, but its retention on the pulp fibers is often poor.Such starch granules can gelatinize during the drying process, impartingstiffness and strength to the paper web once it is dry. Adding starchgranules in this manner requires lower amounts of energy to dry thepaper web, while also eliminating or reducing the use of a size press.Moreover, the contamination of the whitewater with gelatinized starchleads to increased biological oxygen demand of the effluent, so that theprocess is environmentally unfavorable.

Starch as a bonding agent between the fibers can also be incorporated inthe form of ungelatinized starch granules. Ungelatinized starch granulescan be added to the wet end of papermaking, but they are poorlyretained. Such starch granules can gelatinize during the drying process,imparting strength to the paper web once it is dry. Adding starchgranules in this manner requires lower amounts of energy to dry thepaper web, while also eliminating or reducing the use of a size press.As an alternative, ungelatinized starch granules can be incorporated asfillers. In their native state, ungelatinized starch granules do notabsorb water like the gelatinized starches, so they can be applied topaper webs that have not been pre-dried. Moreover, the granules onceincorporated in the fiber matrix, gelatinize locally thereby acting asinternal bonding between fiber joints without adequately impacting thebulking of the paper. To apply ungelatinized starch, these granules canbe sprayed on the moving moist web, and gelatinization can be effectedin the dryer. This yields an improvement in dry strength and stiffnessof the paper. However, the spraying process does not disperse starchuniformly throughout the thickness of the paper, leading to anisotropicstiffness and strength properties.

There remains a need in the art, therefore, for systems and methods forincorporating and retaining ungelatinized starch fillers in the wet endso that high amounts of these fillers are dispersed uniformly in thepaper. These fillers should, desirably, be incorporated so that they arestably anchored to the pulp fibers, allowing them to expand orgelatinize during paper manufacturing without being dislodged. In thismanner, the fillers can occupy the interstitial spaces between cellulosefibers more completely, improving the rigidity of the paper product.Furthermore, it is known that high filler content has a detrimentaleffect on the strength of the wet web before it is dried because thefillers act as spacers and interfere with fiber-fiber bonding. Anefficient retention system that attaches the fillers to fibers durablyin the wet web can advantageously enhance wet web strength duringprocessing by allowing fiber-fiber bonding to proceed unimpeded.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 shows a graph comparing strength with starch loading.

FIG. 2 shows a graph comparing strength with starch retention.

FIG. 3 shows tensile strength of paper samples.

FIG. 4 shows results from hydrophobicity tests on paper samples.

FIG. 5 shows a flow chart for a papermaking system.

FIG. 6 shows caliper of paper sheets.

FIG. 7 shows tensile strength and caliper for paper sheets.

SUMMARY

Disclosed herein, in embodiments, are systems for papermaking,comprising a population of cellulose fibers dispersed in an aqueoussolution and complexed with an activator, and a tether-bearingparticulate additive, wherein the addition of the tether-bearingparticulate additive attaches the additive to the population ofcellulose fibers by the interaction of the activator and the tether.Also disclosed herein in embodiments, is a papermaking precursorcomprising a population of cellulose fibers in an aqueous solutionwherein the population of cellulose fibers is dispersed in the aqueoussolution and wherein the cellulose fibers are complexed with anactivator, and wherein the aqueous solution further comprises atether-bearing particulate additive, wherein the tether-bearingparticulate additive attaches to the population of cellulose fibers byan interaction between the activator and the tether. In embodiments, theparticulate additive can be an organic additive. In embodiments, theorganic additive can comprise starch, and the starch can be a cationicstarch or a hydrophobic starch. In other embodiments, the particulateadditive can be an inorganic additive.

Also disclosed herein are systems for papermaking, comprising a firstset of processing stations, wherein a papermaking precursor is formed bycombining a population of cellulose fibers dispersed in an aqueoussolution and complexed with an activator, and a tether-bearingparticulate additive, and wherein the addition of the tether-bearingparticulate additive attaches the additive to the population ofcellulose fibers by the interaction of the activator and the tether; anda second set of processing stations. In embodiments, the particulateadditive can be an organic additive. In embodiments, the organicadditive can comprise starch, and the starch can be a cationic starch ora hydrophobic starch. In other embodiments, the particulate additive canbe an inorganic additive.

Further disclosed herein are methods for manufacturing a paper product,comprising activating a population of cellulose fibers with anactivator, preparing a tether-bearing particulate additive, wherein thetether-bearing particulate additive comprises a tether capable ofinteracting with the activator; and adding the tether-bearingparticulate additive to the activated population of cellulose fibers,thereby attaching the additive to the fibers by the interaction of theactivator and the tether. In embodiments, methods are disclosed hereinfor increasing the strength of a paper product formed from a pulp slurrycomprising cellulose fibers, comprising adding an activator polymer tothe pulp slurry, forming complexes between the activator polymer andcellulose fibers in the pulp slurry, preparing tether-bearing starchgranules, wherein the tether-bearing starch granules comprise a tetherpolymer capable of interacting with the activator polymer, and addingthe tether-bearing starch granules to the pulp slurry, whereby thestarch granules are attached to the cellulose fibers by the interactionof the activator polymer and the tether polymer, thereby increasing thestrength of the paper product formed from the pulp slurry. Furtherdisclosed herein are paper products manufactured in accordance withthese methods.

Also disclosed herein, in embodiments, are methods for increasing thebulk of a paper product formed from a pulp slurry comprising cellulosefibers, comprising: providing a first population of cellulose fiberscomprising unrefined softwood fibers, forming a first slurry comprisingthe first population, adding an activator polymer to the first slurry,forming complexes between the activator polymer and the cellulosefibers, providing a second population of cellulose fibers comprisinghardwood fibers, forming a second slurry comprising the secondpopulation, preparing tether-bearing starch granules, wherein thetether-bearing starch granules comprise a tether polymer capable ofinteracting with the activator polymer, combining the tether-bearingstarch granules with the second slurry whereby the tether-bearing starchgranules attach to the hardwood fibers, and adding the second slurry tothe first slurry to form a pulp slurry, whereby the starch granulesattach the hardwood fibers to the softwood fibers in the pulp slurry,thereby improving a measure of bulk of a paper product formed from thepulp slurry. In certain embodiments, methods are disclosed forincreasing the bulk of a paper product formed from a pulp slurrycomprising cellulose fibers, comprising providing a cellulose fibermixture, forming a slurry comprising the cellulose fiber mixture, addingan activator polymer to the slurry to form an activated mixturecomprising activated cellulose fibers, preparing tether-bearing starchgranules, wherein the tether-bearing starch granules comprise a tetherpolymer capable of interacting with the activator polymer, combining thetether-bearing starch granules with the activated fiber mixture, wherebythe tether-bearing starch granules affix the activated cellulose fibersto each other, thereby increasing the bulk of the paper product formedtherefrom. In embodiments, the cellulose fiber mixture compriseshardwood and softwood fibers. In embodiments, the cellulose fibermixture comprises refined and unrefined fibers. Further disclosed hereinare paper products manufactured in accordance with these methods.

DETAILED DESCRIPTION

Disclosed herein are systems, precursors, and methods for enhancing theattachment of a particulate additive to a fibrous matrix, so that theparticles are efficiently and durably attached to the coarser fibrousmatrix. Also disclosed herein are processes for manufacturing a paperproduct by forming a complex between a particulate additive (such asstarch) and the fibers. The invention also encompasses paper made by theprocesses or method described herein or from a precursor describedherein. The systems and methods disclosed herein involve threecomponents: activating the fibers as they are dispersed in a solution,attaching a tethering agent to the particulate additive, and adding thetether-bearing particulate additive to the dispersion containing theactivated fibers, so that the additive is attached to the fibers by theinteraction of the activating agent and the tethering agent. Inembodiments, these systems and methods can be used to treat fibers usedin papermaking with a cationic polymer of a specific molecular weightand composition as an activator, to treat starch granules with ananionic polymer as a tethering agent, and to combine theseseparately-treated populations so that the starch granules are attachedto the pulp fibers.

1. Activation

As used herein, the term “activation” refers to the interaction of anactivating material, such as a polymer, with suspended particles orfibers in a liquid medium, such as an aqueous solution. An “Activatorpolymer” can carry out this activation. In embodiments, high molecularweight polymers can be introduced into the particulate or fibrousdispersion as Activator polymers, so that these polymers interact, orcomplex, with the dispersed particles or fibers. The polymer-fibercomplexes interact with other similar complexes, or with other fibers,and form agglomerates.

This “activation” step can function as a pretreatment to prepare thesurface of the suspended material (e.g., fibers) for furtherinteractions in the subsequent phases of the disclosed system andmethods. For example, the activation step can prepare the surface of thesuspended materials to interact with other polymers that have beenrationally designed to interact therewith in a subsequent “tethering”step, as described below. Not to be bound by theory, it is believed thatwhen the suspended materials (e.g., fibers) are coated by an activatingmaterial such as a polymer, these coated materials can adopt some of thesurface properties of the polymer or other coating. This altered surfacecharacter in itself can be advantageous for retention, attachment and/ordewatering.

In another embodiment, activation can be accomplished by chemicalmodification of the suspended material. For example, oxidants orbases/alkalis can increase the negative surface energy of fibers orparticles, and acids can decrease the negative surface energy or eveninduce a positive surface energy on suspended material. In anotherembodiment, electrochemical oxidation or reduction processes can be usedto affect the surface charge on the suspended materials. These chemicalmodifications can produce activated particulates that have a higheraffinity for tethered anchor particles as described below.

Suspended materials suitable for modification, or activation, caninclude organic or inorganic particles, or mixtures thereof. Inorganicparticles can include one or more materials such as calcium carbonate,dolomite, calcium sulfate, kaolin, talc, titanium dioxide, sand,diatomaceous earth, aluminum hydroxide, silica, other metal oxides andthe like. Organic particles can include one or more materials such asstarch, modified starch, polymeric spheres (both solid and hollow),carbon based nanoparticles such as carbon nanotubes and the like.Particle sizes can range from a few nanometers to a few hundred microns.In certain embodiments, macroscopic particles in the millimeter rangemay be suitable.

In embodiments, suspended materials may comprise materials such aslignocellulosic material, cellulosic material, minerals, vitreousmaterial, cementitious material, carbonaceous material, plastics,elastomeric materials, and the like. In embodiments, cellulosic andlignocellulosic materials may include wood materials such as woodflakes, wood fibers, wood waste material, wood powder, lignins, woodpulp, or fibers from woody plants.

The “activation” step may be performed using flocculants or otherpolymeric substances. Preferably, the polymers or flocculants can becharged, including anionic or cationic polymers.

In embodiments, anionic polymers can be used, including, for example,olefinic polymers, such as polymers made from polyacrylate,polymethacrylate, partially hydrolyzed polyacrylamide, and salts, estersand copolymers thereof (such as sodium acrylate/acrylamide copolymers),sulfonated polymers, such as sulfonated polystyrene, and salts, estersand copolymers thereof. Suitable polycations include: polyvinylamines,polyallylamines, polydiallyldimethylammoniums (e.g., the chloride salt),branched or linear polyethyleneimine, crosslinked amines (includingepichlorohydrin/dimethylamine, and epichlorohydrin/alkylenediamines),quaternary ammonium substituted polymers, such as(acrylamide/dimethylaminoethylacrylate methyl chloride quat) copolymersand trimethylammoniummethylene-substituted polystyrene, and the like.Nonionic polymers suitable for hydrogen bonding interactions can includepolyethylene oxide, polypropylene oxide, polyhydroxyethylacrylate,polyhydroxyethylmethacrylate, and the like. In embodiments, an activatorsuch as polyethylene oxide can be used as an activator with a cationictethering material in accordance with the description of tetheringmaterials below. In embodiments, activator polymers with hydrophobicmodifications can be used. Flocculants such as those sold under thetrademark MAGNAFLOC® by Ciba Specialty Chemicals can be used.

In embodiments, activators such as polymers or copolymers containingcarboxylate, sulfonate, phosphonate, or hydroxamate groups can be used.These groups can be incorporated in the polymer as manufactured,alternatively they can be produced by neutralization of thecorresponding acid groups, or generated by hydrolysis of a precursorsuch as an ester, amide, anhydride, or nitrile group. The neutralizationor hydrolysis step could be done on site prior to the point of use, orit could occur in situ in the process stream.

The activated suspended material (e.g., fiber) can also be an aminefunctionalized or modified material. As used herein, the term “modifiedmaterial” can include any material that has been modified by theattachment of one or more amine functional groups as described herein.The functional group on the surface of the suspended material can befrom modification using a multifunctional coupling agent or a polymer.The multifunctional coupling agent can be an amino silane coupling agentas an example. These molecules can bond to a material's surface and thenpresent their amine group for interaction with the particulate matter.In the case of a polymer, the polymer on the surface of a suspendedfiber or particle can be covalently bound to the surface or interactwith the surface of the particle and/or fiber using any number of otherforces such as electrostatic, hydrophobic, or hydrogen bondinginteractions. In the case that the polymer is covalently bound to thesurface, a multifunctional coupling agent can be used such as a silanecoupling agent. Suitable coupling agents include isocyano silanes andepoxy silanes as examples. A polyamine can then react with an isocyanosilane or epoxy silane for example. Polyamines include polyallyl amine,polyvinyl amine, chitosan, and polyethylenimine.

In embodiments, polyamines (polymers containing primary, secondary,tertiary, and/or quaternary amines) can also self-assemble onto thesurface of the suspended particles or fibers to functionalize themwithout the need of a coupling agent. For example, polyamines canself-assemble onto the surface of the particles or fibers throughelectrostatic interactions. They can also be precipitated onto thesurface in the case of chitosan for example. Since chitosan is solublein acidic aqueous conditions, it can be precipitated onto the surface ofsuspended material by adding a chitosan solution to the suspendedmaterial at a low pH and then raising the solution pH.

In embodiments, the amines or a majority of amines are charged. Somepolyamines, such as quarternary amines are fully charged regardless ofthe pH. Other amines can be charged or uncharged depending on theenvironment. The polyamines can be charged after addition onto thesuspended particles or fibers by treating them with an acid solution toprotonate the amines. In embodiments, the acid solution can benon-aqueous to prevent the polyamine from going back into solution inthe case where it is not covalently attached to the particle or fiber.

The polymers or particles can complex via forming one or more ionicbonds, covalent bonds, hydrogen bonding and combinations thereof, forexample. Ionic complexing is preferred.

To obtain activated suspended materials, the activator could beintroduced into a liquid medium through several different means. Forexample, a large mixing tank could be used to mix an activating materialwith fine particulate materials. Activated particles or fibers areproduced that can be treated with one or more subsequent steps ofattachment to tether-bearing anchor particles.

2. Tethering

As used herein, the term “tethering” refers to an interaction between anactivated suspended particle or fiber and an anchor particle (asdescribed below). The anchor particle can be treated or coated with atethering material. The tethering material, such as a polymer, forms acomplex or coating on the surface of the anchor particles such that thetethered anchor particles have an affinity for the activated suspendedmaterial. In embodiments, the selection of tether and activatormaterials is intended to make the two solids streams complementary sothat the activated particles or fibers in the suspension becometethered, linked or otherwise attached to the anchor particle.

In accordance with these systems and methods, the tethering materialacts as a complexing agent to affix the activated particles or fibers toan anchor material. In embodiments, a tethering material can be any typeof material that interacts strongly with the activating material andthat is connectable to an anchor particle.

In embodiments, an anchor particle may comprise materials such aslignocellulosic material, cellulosic material, minerals, vitreousmaterial, cementitious material, carbonaceous material, plastics,elastomeric materials, and the like. In embodiments, cellulosic andlignocellulosic materials may include wood materials such as woodflakes, wood fibers, wood waste material, wood powder, lignins, orfibers from woody plants.

Examples of inorganic particles useful as anchor particles include clayssuch as attapulgite and bentonite. In embodiments, the inorganiccompounds can be vitreous materials, such as ceramic particles, glass,fly ash, PCC, GCC, chalk, TiO₂, silica, bentonite, kaolin, talc, and thelike. The anchor particles may be solid or may be partially orcompletely hollow. For example, glass or ceramic microspheres may beused as particles. Vitreous materials such as glass or ceramic may alsobe formed as fibers to be used as particles. Cementitious materials mayinclude gypsum, Portland cement, blast furnace cement, alumina cement,silica cement, and the like. Carbonaceous materials may include carbonblack, graphite, carbon fibers, carbon microparticles, and carbonnanoparticles, for example carbon nanotubes.

In embodiments, plastic materials may be used as anchor particles. Boththermoset and thermoplastic resins may be used to form plasticparticles. Plastic particles may be shaped as solid bodies, hollowbodies or fibers, or any other suitable shape. Plastic particles can beformed from a variety of polymers. A polymer useful as a plasticparticle may be a homopolymer or a copolymer. Copolymers can includeblock copolymers, graft copolymers, and interpolymers. In embodiments,suitable plastics may include, for example, addition polymers (e.g.,polymers of ethylenically unsaturated monomers), polyesters,polyurethanes, aramid resins, acetal resins, formaldehyde resins, andthe like. Addition polymers can include, for example, polyolefins,polystyrene, and vinyl polymers. Polyolefins can include, inembodiments, polymers prepared from C₂-C₁₀ olefin monomers, e.g.,ethylene, propylene, butylene, dicyclopentadiene, and the like. Inembodiments, poly(vinyl chloride) polymers, acrylonitrile polymers, andthe like can be used. In embodiments, useful polymers for the formationof particles may be formed by condensation reaction of a polyhydriccompound (e.g., an alkylene glycol, a polyether alcohol, or the like)with one or more polycarboxylic acids. Polyethylene terephthalate is anexample of a suitable polyester resin. Polyurethane resins can include,e.g., polyether polyurethanes and polyester polyurethanes. Plastics mayalso be obtained for these uses from waste plastic, such aspost-consumer waste including plastic bags, containers, bottles made ofhigh density polyethylene, polyethylene grocery store bags, and thelike.

In embodiments, plastic particles for anchor particles can be formed asexpandable polymeric pellets. Such pellets may have any geometry usefulfor the specific application, whether spherical, cylindrical, ovoid, orirregular. Expandable pellets may be pre-expanded before using them.Pre-expansion can take place by heating the pellets to a temperatureabove their softening point until they deform and foam to produce aloose composition having a specific density and bulk. Afterpre-expansion, the particles may be molded into a particular shape andsize. For example, they may be heated with steam to cause them to fusetogether into a lightweight cellular material with a size and shapeconforming to the mold cavity. Expanded pellets may be 2-4 times largerthan unexpanded pellets. As examples, expandable polymeric pellets maybe formed from polystyrenes and polyolefins. Expandable pellets areavailable in a variety of unexpanded particle sizes. Pellet sizes,measured along the pellet's longest axis, on a weight average basis, canrange from about 0.1 to 6 mm.

In embodiments, the expandable pellets may be formed by polymerizing thepellet material in an aqueous suspension in the presence of one or moreexpanding agents, or by adding the expanding agent to an aqueoussuspension of finely subdivided particles of the material. An expandingagent, also called a “blowing agent,” is a gas or liquid that does notdissolve the expandable polymer and which boils below the softeningpoint of the polymer. Blowing agents can include lower alkanes andhalogenated lower alkanes, e.g., propane, butane, pentane, cyclopentane,hexane, cyclohexane, dichlorodifluoromethane, andtrifluorochloromethane, and the like. Depending on the amount of blowingagent used and the technique for expansion, a range of expansioncapabilities exist for any specific unexpanded pellet system. Theexpansion capability relates to how much a pellet can expand when heatedto its expansion temperature. In embodiments, elastomeric materials canbe used as particles. Particles of natural or synthetic rubber can beused, for example.

In embodiments, various interactions such as electrostatic, hydrogenbonding or hydrophobic behavior can be used to affix an activatedcomplex to a tethering material complexed with an anchor particle.

For use in papermaking, an anchor particle can be selected from anyparticulate matter that is desirably attached to cellulose fibers in thefinal paper product. The tether-bearing anchor particle comprising thedesirable additive can then interact with the activated cellulose fibersin the wet paper stream. As an example, starch granules can be used asan anchor particle to be attached to the cellulose fibers, as isdescribed in more detail below. In other examples, organic and inorganicparticulate matter can be attached to celluose fibers to achieve desiredproperties. For example, inorganic materials like calcium carbonate,dolomite, calcium sulfate, kaolin, talc, titanium dioxide, sand,diatomaceous earth, aluminum hydroxide, silica, various other metaloxides, and the like, can be used as anchor particles in accordance withthese systems and methods. In other embodiments, organic particles suchas starch, modified starch, polymeric spheres (both solid and hollow),carbon based nanoparticles such as carbon nanotubes and the like, can beused as anchor particles in accordance with these systems and methods.

In embodiments, polymers such as linear or branched polyethyleneiminecan be used as tethering materials. It would be understood that otheranionic or cationic polymers could be used as tethering agents, forexample polydiallyldimethylammonium chloride (poly(DADMAC)). In otherembodiments, cationic tethering agents such as epichlorohydrindimethylamine (epi/DMA), styrene maleic anhydride imide (SMAI),polyethylene imide (PEI), polyvinylamine, polyallylamine, amine-aldehydecondensates, poly(dimethylaminoethyl acrylate methyl chloridequaternary) polymers and the like can be used. Advantageously, cationicpolymers useful as tethering agents can include quaternary ammonium orphosphonium groups. Advantageously, polymers with quaternary ammoniumgroups such as poly(DADMAC) or epi/DMA can be used as tethering agents.In other embodiments, polyvalent metal salts (e.g., calcium, magnesium,aluminum, iron salts, and the like) can be used as tethering agents. Inother embodiments cationic surfactants such asdimethyldialkyl(C8-C22)ammonium halides, alkyl(C8-C22)trimethylammoniumhalides, alkyl(C8-C22)dimethylbenzylammonium halides, cetyl pyridiniumchloride, fatty amines, protonated or quaternized fatty amines, fattyamides and alkyl phosphonium compounds can be used as tethering agents.In embodiments, polymers having hydrophobic modifications can be used astethering agents.

The efficacy of a tethering material, however, can depend on theactivating material. A high affinity between the tethering material andthe activating material can lead to a strong and/or rapid interactionthere between. A suitable choice for tether material is one that canremain bound to the anchor surface, but can impart surface propertiesthat are beneficial to a strong complex formation with the activatorpolymer. For example, a polyanionic activator can be matched with apolycationic tether material or a polycationic activator can be matchedwith a polyanionic tether material. In one embodiment, a poly(sodiumacrylate-co-acrylamide) activator is matched with a chitosan tethermaterial.

In hydrogen bonding terms, a hydrogen bond donor should be used inconjunction with a hydrogen bond acceptor. In embodiments, the tethermaterial can be complementary to the chosen activator, and bothmaterials can possess a strong affinity to their respective depositionsurfaces while retaining this surface property.

In other embodiments, cationic-anionic interactions can be arrangedbetween activated suspended materials and tether-bearing anchorparticles. The activator may be a cationic or an anionic material, aslong as it has an affinity for the suspended material to which itattaches. The complementary tethering material can be selected to haveaffinity for the specific anchor particles being used in the system. Inother embodiments, hydrophobic interactions can be employed in theactivation-tethering system.

As would be further appreciated by those of ordinary skill,tether-bearing anchor particles could be designed to complex with aspecific type of activated particulate matter. The systems and methodsdisclosed herein could be used for complexing with organic wasteparticles, for example. Other activation-tethering-anchoring systems maybe envisioned for removal of suspended particulate matter in fluidstreams, including gaseous streams.

3. Retention and Incorporation in Papermaking

It is envisioned that the complexes formed from the anchor particles andthe activated fibrous matter can form a homogeneous part of a fibrousproduct like paper. In embodiments, the interactions between theactivated suspended fibers and the tether-bearing anchor particles canenhance the mechanical properties of the complex that they form. Forexample, an activated suspended material can be durably bound to one ormore tether-bearing anchor particles, so that the tether-bearing anchorparticles do not segregate or move from their position on the fibers.Increased compatibility of the activated fine materials with a denser(anchor) matrix modified with the appropriate tether polymer can lead tofurther mechanical stability of the resulting composite material.

For papermaking, cationic and anionic polymers for activators andtethering agents (respectively) can be selected from a wide variety ofavailable polymers, as described above. Starch granules or otherdesirable particles can be selected as anchor particles, where theirattachment to pulp fibers would be advantageous. Examples of suchdesirable particles include, but are not limited to inorganic andorganic anchor particles such as have been described above (e.g., forinorganic materials, calcium carbonate, dolomite, calcium sulfate,kaolin, talc, titanium dioxide, sand, diatomaceous earth, aluminumhydroxide, silica, various other metal oxides and the like, and fororganic materials, starch, modified starch, polymeric spheres (bothsolid and hollow), carbon based nanoparticles such as carbon nanotubesand the like). When starch granules are used as anchor particles forattachment to cellulose fibers, they can be used in their native state,or they can be modified with short amine side-groups, with aminepolymers, or with hydrophobic side groups (each a “modified starch”).The presence of amines on the surface of the starch granules can help inattaching an anionic tethering polymer.

For activating the cellulose fibers, cationic polymers can be used. Thepolycation can be linked to the fiber surface using a coupling agent,for example a bifunctional crosslinking agent such as acarbonyldiimidazole or a silane, or the polyamine can self-assemble ontothe surface of the cellulose fiber through electrostatic, hydrogenbonding, or hydrophobic interactions. In embodiments, the polyamine canspontaneously self-assemble onto the fiber surface or it can beprecipitated onto the surface. For example, in embodiments, chitosan canbe precipitated on the surface of the cellulose fibers to activate them.Because chitosan is soluble only in an acidic solution, it can be addedto a cellulose fiber dispersion at an acidic pH, and then can beprecipitated onto the surface of the cellulose fibers by slowly addingbase to the dispersion until chitosan is no longer soluble. Inembodiments, a difunctional crosslinking agent can be used to attach thepolycation to the fiber, by reacting with both the polycation and thefiber.

In other embodiments, a polycation such as a polyamine can be addeddirectly to the fiber dispersion or slurry. For example, the additionlevel of the polycation can be between about 0.01% to 5.0% (based on theweight of the fiber), e.g., between 0.1% to 2%. For example, if thecellulose fiber population is treated with a polyamine like polyDADMAC,a separately treated population of tether-bearing starch granules can bemixed in thereafter, resulting in the attachment of the starch granulesto the cellulose fibers by the interaction of the activator polymer andthe tether polymer. Starch granules can be treated with a variety ofanionic polymers, such as anionic polyacrylamide, which then act astethers.

While individual retention aids such as polyacrylamide are known in theart to help with the retention of starch granules within a cellulosematrix, the drainage of the paper web is severely affected by the use ofthese agents individually. The use of a complementary polycation (e.g.,polyDADMAC) as an activator, combined with the use of the polyanion as atether attached to the starch granules in accordance with these systemsand methods avoids this problem, reducing the water retention in thepaper web and leading to efficient drainage. Furthermore, the use ofthese systems and methods eliminates the requirement for cooking thestarch before using it, thereby eliminating the gelatinizing (“cooking”)step, and decreasing energy utilization.

Starch that is to be treated in accordance with these systems andmethods can be further derivatized or coated with moieties that impartdesirable properties, e.g., hydrophobicity, oleophobicity or both.Starches thus modified may be also termed “modified starches.” Preferredoil resistant coating formulations are aqueous solutions of cellulosederivatives such as methylcellulose, ethyl cellulose, propyl cellulose,hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose,ethylhydroxypropyl cellulose, and ethylhydroxyethyl cellulose, celluloseacetate butyrate, which may further comprise polyvinyl alcohol and/orits derivatives. Another group of preferred oil resistant coatingcompositions are latex emulsions such as the emulsions of polystyrene,styrene-acrylonitrile copolymer, carboxylated styrene-butadienecopolymer, ethylene-vinyl chloride copolymer, styrene-acrylic copolymer,polyvinyl acetate, ethylene-vinyl acetate copolymer, and vinylacetate-acrylic copolymer. The starch granule thus coated with greaseresistant formulations could be attached to the activated pulp fibersvia tethering, such that the surface segregation of the starch granulewill modify the surface of the paper product.

In embodiments, the presence of hydrophobic starch also improves thehydrophobicity of the resulting paper without needing an internal sizingsuch as alkyl succinic anhydride (ASA), alkyl ketene dimer (AKD) orRosin. The gelatinized hydrophobic starch sizes the entire thickness ofthe paper. This property is useful in reducing the coating requirementsin making coated sheets. The coating applied using a roller or ametering bar or any such methods, would remain on the surface of thepaper and not impregnate the bulk of the paper thus needing less coatingto achieve the same amount of gloss and surface finish.

In other embodiments, the addition of a coating agent to the starch canimprove its mechanical properties such as bending stiffness or tensilestrength, or could improve its optical properties (e.g., TiO2nanoparticles bound to starch).

4. Bulk Enhancement

It is known in the art that the use of refined softwood fibers resultsin a stronger paper matrix than the use of unrefined softwood fibers.The refining process, though, changes the geometry of the long(softwood) fibers from a three-dimensional cylindrical structure to aflat ribbon-like structure. The refining process thus diminishes theoverall bulk of the paper product. Refining also requires a significantamount of energy to treat the pulp mechanically to produce the flatter,denser pulp fibers. Paper products are typically formed from a certainpercentage of refined pulp, ranging from 0% to 100% refined pulp, toproduce a sheet of the desired strength.

It is also known in the art that recycled pulp can be used to form paperproducts. As used herein, the term “paper products” refers to a productmade from natural cellulose fibers, such as hardwood, softwood orrecycled fibers. For example, certain paper products for packagingapplications can be made from recycled fibers, e.g., cardboard andcorrugated board. These packaging products need a combination of bulkand stiffness to effective during stacked storage and shipment. Therecycling process truncates the length of the fibers and reduces boththe bulk and strength. One way to improve strength is by refining therecycled fibers which further reduces bulk. Bulking with stiffnessimprovement also allows for reducing packaging weight by using lessfibers to attain a required bulk and stiffness.

Recycled fibers can be derived from hardwood could be made from bothhardwood and softwood depending on the source of the paper product.

As used herein, the term “papermaking” refers to the formation of apaper product using hardwood fibers, softwood fibers, recycled fibers orany combination thereof. As used herein, the term “cellulose mixture”refers to any mixture of natural cellulose fibers, whether hardwood,softwood or recycled. A “papermaking precursor” is a solution or mixturecomprising cellulose fibers, wherein the solution or mixture has notbeen subjected to complete drying.

Use of granulated starch, in accordance with the foregoing systems andmethods, results in a stronger paper product. In addition, it has beenunexpectedly discovered that the use of granulated starch can alsoreduce or even eliminate the need for refined pulp in papermaking,thereby yielding a higher bulk sheet. A number of processing schematacan be employed to enhance bulk during papermaking in accordance withthese systems and methods.

As shown schematically in FIG. 5, an exemplary papermaking system 100can involve a number of processing stations, 102, 104, 108, 110, 112,114, 118, 120, and 122. In a pulp mill 102, wood chips are broken downmechanically or chemically, and may be bleached. For recycled paper, thepulp-based components are repulped in a pulp mill 102. Additives may beadded to the pulp stream as it exits the pulp mill 102, as shown atPoint C. The processed pulp can then proceed to a refiner 104, where thepulp is mechanically treated to increase surface area of fibers, therebyincreasing bonding between fibers, resulting in flatter, denser pulpfibers. Additives may be added to the pulp stream as it exits therefiner 104, as shown at Point A. The pulp stream can then proceed to amachine chest 108, where the pulp comes into contact with certainchemicals used in papermaking. This processing station 108 is wheremulti-stream pulps can meet and become admixed (e.g., hardwood andsoftwood pulp). Additives may be added to the pulp stream as it exitsthe machine chest, as shown at Point B. The pulp stream can then proceedto the headbox 110, where the pulp can be diluted further and releasedfrom the headbox onto the forming wire. The first set of processingstations 102-110 comprise the wet end of a papermaking system ormachine. The pulp stream can then proceed to a second set of processingstations for forming the paper sheet. These processing stations caninclude a vacuum section 112, a press section 114, a first dryingsection 118, a size press 120, and a second drying section 122. In thevacuum section 112, the fiber web can be drained by gravity and then byhigh vacuum to about 10-15% solids. The fiber web can then proceed to apress section 114, where the formed fiber web can be pressed throughhigh-pressure rollers to a consistency of about 20-25% solids. The wetpaper web can then proceed to a first drying section 118, where the wetpaper web can make contact with steam-heated dryers that contact-dry thesheet up to 98% solids. The paper sheet can then proceed to a size press120, where gelatinized starch and other chemicals can be applied to thesurface of the paper. The paper sheet can then proceed to a seconddrying section 122, where a second set of dryers dry the sheet after ithas been wetted in the size press 120.

In embodiments, additives can be added at Points A, B, and/or C toimprove the quality of paper product emerging from a papermaking system100. A pulp product combined with the activator polymer andtether-bearing anchor particles as described below is a specific exampleof a “papermaking precursor.” In one embodiment, an activator polymercan be added at Point A, and tether-bearing anchor particles comprisinga desirable additive (e.g., a starch) can be added at Point B. Inanother embodiment, an activator polymer can be added to a softwoodstream only at Point A, which can then be admixed with a second stream(e.g., a hardwood stream) in the machine chest 108 or comparablecomponent of the papermaking system 100. In this embodiment,tether-bearing anchor particles comprising a desirable additive (e.g., astarch) can be added at Point B. In another embodiment, an activatorpolymer can be added to a hardwood stream only at Point A, which canthen be admixed with a second stream (e.g., a softwood stream) in themachine chest 108 or comparable component of the papermaking system 100.In this embodiment, tether-bearing anchor particles comprising adesirable additive (e.g., a starch) can be added at Point B. In yetanother embodiment, an activator polymer can be added to a hardwoodstream at Point C, and the activated stream proceeds through the refiner104; this activated hardwood stream can be admixed with a second stream(e.g., a softwood stream) in the machine chest 108 or comparablecomponent of the papermaking system 100. In this embodiment,tether-bearing anchor particles comprising a desirable additive (e.g., astarch) can be added at Point B. In yet another embodiment, an activatorpolymer can be added to a softwood stream at Point C, and the activatedstream proceeds through the refiner 104; this activated softwood streamcan be admixed with a second stream (e.g., a hardwood stream) in themachine chest 108 or comparable component of the papermaking system 100.In this embodiment, tether-bearing anchor particles comprising adesirable additive (e.g., a starch) can be added at Point B, or at PointA. In yet another embodiment, an activator polymer can be added to ahardwood stream at Point C, and the activated stream proceeds throughthe refiner 104; this activated hardwood stream can be admixed with asecond stream (e.g., a softwood stream) in the machine chest 108 orcomparable component of the papermaking system 100. In this embodiment,tether-bearing anchor particles comprising a desirable additive (e.g., astarch) can be added at Point B, or at Point A. In another embodiment,an activator polymer can be added at Point C, and the activated streamproceeds through the refiner 104. In this embodiment, tether-bearinganchor particles comprising a desirable additive (e.g., a starch) can beadded at Point B, or at Point A.

As would be understood by skilled artisans, a combination of hardwoodand softwood fibers in a pulp mixture may be desirable, and that acombination of refined and unrefined fibers (either hardwood orsoftwood) may be desirable. Without being bound by theory, it isunderstood that unrefined fibers offer bulk and refined fibers offerstrength in the final paper sheet. In embodiments, a cellulose fibermixture containing between about 10% and about 90% hardwood can be used.In other embodiments, a cellulose fiber mixture containing between about40% and about 80% hardwood can be used. In other embodiments, acellulose fiber mixture containing between about 60% and about 80%hardwood can be used, or between about 65% and about 75%. Inembodiments, a cellulose fiber mixture containing between about 5% andabout 75% unrefined fibers can be used. In other embodiments, acellulose fiber mixture containing between about 20% and about 60%unrefined fibers can be used. In other embodiments, a cellulose fibermixture containing between about 30% and about 50% unrefined fibers canbe used.

EQUIVALENTS

While specific embodiments of the subject invention have been discussed,the above specification is illustrative and not restrictive. Manyvariations of the invention will become apparent to those skilled in theart upon review of this specification. Unless otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions, andso forth used in the specification and claims are to be understood asbeing modified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thisspecification and attached claims are approximations that can varydepending upon the desired properties sought to be obtained by thepresent invention.

EXAMPLES

Materials

Market softwood and hardwood pulp

Recycled and deinked pulp from magazine and newsprint

Poly(diallyldimethylammonium chloride), Hi Molecular Weight, 20 wt % inwater (polyDADMAC), Sigma-Aldrich, St. Louis, Mo.

MagnaFloc LT30 (PAM) Ciba Specialty Chemicals Corporation, Suffolk, Va.

STA-LOK 356 Starch, Tate & Lyle, Decatur, Ill. (cationic starchgranules)

ChitoClear Chitosan CG800, Primex, Siglufjordur, Iceland

Lupamin 9095, BASF Corporation, Florham Park, N.J.

R465 Cationic Starch, Grain Processing Corporation, Muscatine, Iowa

FilmKote hydrophobic starches, National Starch LLC, Bridgewater N.J.

Example 1 Control Virgin Pulp

A 0.5% slurry was prepared by blending 3.5% by weight softwood andhardwood pulp mixture (in the ratio of 20:80) in water.

Example 2 Control Recycled Pulp

A 0.5% slurry was prepared by blending 3.1% recycled deinked pulp inwater.

Example 3 Handsheet Preparation

Handsheets were prepared using a Mark V Dynamic Paper Chemistry Jar andHand-Sheet Mold from Paper Chemistry Laboratory, Inc. (Larchmont, N.Y.).Handsheets were prepared without addition of polymers as controls, usingthe control pulps as described in Example 1 and 2. Handsheets wereprepared with the addition of polymers as experimental samples, asdescribed below. For preparing each experimental handsheet, theappropriate volume of 0.5% pulp slurry prepared in accordance withExamples 1 or 2 (as applicable) was activated with up to 2% of theselected polymer(s) (based on dry weight), as described below in moredetail. Polymer additions were performed at 5 minute intervals. Thispolymer-containing slurry was diluted with up to 2 L of water and addedto the handsheet maker, where it was mixed at a rate of 1100 RPM for 5seconds, 700 RPM for 5 seconds, and 400 RPM for 5 seconds. The water wasthen drained off. The subsequent sheet was then transferred off of thewire, pressed and dried.

Example 4 Tensile Test

Tensile tests were conducted on control and experimental samples usingan Instron 3343. Samples of handsheets for tensile testing wereinitially cut into 1 in wide strips with a paper cutter, then attachedwithin the Instron 3343. The gauge length region was set at 4 in and thecrosshead speed was 1 in/minute. Thickness was measured to providestress data as was the weight to be able to normalize the data by weightof samples. The strips were tested to failure with an appropriate loadcell. At least three strips from each control or experimental handsheetsample were tested and the values were averaged together.

Example 5 Preparation of Tethered Starches

Sta Lok 356 or Filmkote starches were dispersed in water such that thesolids content was about 20 to 25% to get a slurry of cationic andhydrophobic starches respectively. 1% by weight of anionicpolyacrylamide magnafloc LT30 was used as the tethering agent.

Example 6 Process for Preparing Handsheets from Activated Pulp andTethered Starch

800 ml of a 0.5% pulp slurry prepared in accordance with Example 1 or 2(as applicable) was initially provided. The pulp slurry was activatedwith 1% by fiber weight polyDADMAC. Separately, tethered cationic (orhydrophobic) starch granules were prepared as a slurry in accordancewith Example 5. Each slurry was mixed for 5 minutes and then combinedand mixed for another 5 minutes using an overhead stirrer. Handsheetswere then produced by the method in Example 3. The final paper weightwas approximately 4 g for these handsheets.

Example 7 Starch Retention Measurement

Starch retention was determined by first analyzing the effluent createdafter making the handsheets in Example 6. A piece of VWR Grade 413filter paper with 5 μm particle retention was initially dried in an ovenat 110 C to remove any moisture and then weighed. The effluent from thehandsheet preparation carried out in Example 5 was then filtered throughthe paper using vacuum filtration. The filter paper was dried again at110° C. to remove any moisture, and was weighed to determine the lostsolids from the handsheet. These solids included the fines from thepapermaking process and starch granules. To normalize for only thestarch contribution to the effluent, a control experiment was run usingthe effluent from the preparation of a control pulp using the activatorpolymer but no starch addition. The filtered solid content in thecontrol effluent was subtracted from the filtered solid content in thestarch-bearing effluent, to yield the amount of starch therein. Thisamount was used to determine the starch retention of the pulp in Example6.

Example 8 Effect on Starch Retention of Polymeric Retention Aids Addedto Cellulose Pulp-(No Starch Tethering)

Experiments were carried out to evaluate the starch retention effects ofvarious polymers that can be used to functionalize cellulose fibers. Apulp slurry prepared in accordance with Example 1 was treated with thevarious polymers listed in Table 1, at the loading levels listed in theTable. The Table lists the effects of the various cellulose fiberpolymeric treatments on starch retention, where starch retention wasmeasured in accordance with Example 7. The anionic polyacrylamide (LT30) resulted in good starch retention, but was observed during theexperiment to adversely affected the drainage of water.

TABLE 1 Sample % Starch Retention Pulp Starch 51% Chitosan 0.1% 47%Chitosan 0.5% 37% Chitosan 1.0% 42% LT 30 0.1% 75% LT 30 0.5% 93% LT 301.0% 89% DADMAC 0.1% 33% DADMAC 0.5% 31% DADMAC 1.0% 29% Polyvinylamine1.0% 42%

Example 9 The Effect of Starch Loading on Strength

Samples were prepared as in Example 6, where the amount oftether-bearing starch (Sta Lok 356) starch ranged from 0.18 g to 2.0 g,i.e., initial loadings of 4% to 33% of the solids weight. Thetether-bearing starch was prepared in accordance with Example 5. Sampleswere made both with activator and tether and without either activator ortether. For ATA-treated samples, the tether used on the starch was 1%MagnaFloc LT30 by solids and the activator on the pulp was 1% polyDADMACby solids. Starch retention was measured as set forth in Example 7, andthe max load for each sample was measured using an Instron as in Example4. Data were normalized by the mass to show load contribution peroverall solids weight. Graph 1 (FIG. 1) shows the strength improvementwith starch loading with and without the ATA process chemistry. For allsamples functionalized with the ATA chemistry described in Example 6,the starch granule retention was >98%. Without being bound by theory, itis understood that the inclusion of untethered starch in the unactivatedpaper matrix is limited by the amount of physical entanglements betweenstarch and cellulose, reflected in the plateau in strength measurementwith higher loads of starch added without ATA processing. With ATA, agreater amount of starch can be attached effectively to the cellulose,progressively increasing strength as shown in FIG. 1. As the amount ofATA-bound starch increases, it yields a maximum benefit in strength,which then decreases at higher loadings. It is hypothesized that thehigher loadings beyond the maximum exceed the capacity of the hydrogenbonding network of the cellulose fibers.

Example 10 The Effect of Starch Loading on Strength and Hydrophobicity

Samples were prepared as in Example 6 with tether-bearing Sta Lok 356starch. Starch retention was measured as set forth in Example 7, and thetensile strength for each sample was measured using an Instron as inExample 4. As set forth in Table 2, certain of the samples were treatedwith polyDADMAC as activator in concentrations of 1% by solids, and withMagnaFloc LT30 as the tethering agent attached to the starch inconcentrations of 1% by solids all in accordance with Example 6. Thesesamples are designated as ATA Process samples in the table below (Table2).

TABLE 2 Starch Fiber Overall Starch ATA Starch in % Starch Actual StarchTensile # Wt (g) Loading Amt (g) Process effluent (g) Retention LoadingLoad/Wt E 4 0% 0.0000 No 0.009 0% 2.62 F 4 17%  0.8007 No 0.318 60% 11% 3.75 G 4 17%  0.8066 Yes 0.014 98% 17%  4.52 H 4 9% 0.4064 No 0.171 58%6% 3.63 I 4 9% 0.3999 Yes 0.003 99% 9% 4.02 J 4 5% 0.2072 No 0.074 64%3% 3.46 K 4 5% 0.2019 Yes 0.006 97% 5% 3.56

Graph 2 (FIG. 2) illustrates the effect of starch retention on thestrength of the paper. Graph 2 compares the difference between strengthof the handsheets made with the ATA Process compared to handsheets thathave not been treated with any polymer addition.

Example 11 Effect of Hydrophobic Starch Loading on Strength of PaperMade with Recycled Fibers

Recycled fibers are relatively weak due to fiber length reduction duringfiber recovery and processing. In this example, the ATA process isapplied to improve the strength of handsheets made from recycled fibersby incorporating starch within the fibrous web. To produce handsheets ofrecycled paper using the ATA process, a recycled pulp slurry prepared inaccordance with Example 3 was treated in accordance with Example 6,using Filmkote hydrophobic starches as tether-bearing starches. Filmkotestarches of varying degrees of hydrophobicity were used, as set forth inGraph 3 (FIG. 3). For example, the starch Filmkote 550 is morehydrophobic than Filmkote 54. The tensile strength of the paper sampleswas measured as set forth in Example 4. As shown in Graph 3 (FIG. 3),the ATA process as applied to recycled paper improved the strength ofthe paper samples by amounts from about 25-40%.

Example 12 Effect of Hydrophobic Starch Loading on Hydrophobicity ofPaper Made with Recycled Fibers

Using recycled fiber handsheet samples prepared as in Example 11,hydrophobicity was tested by depositing a 15 microliter water droplet onthe surface of the paper and recording the time for the droplet tocompletely absorbed by the paper. The results of the hydrophobicitytests are shown in Graph 4 (FIG. 4). These results demonstrate that theuse of the ATA process to attach hydrophobic starches to recycled pulpfibers improves the water resistance of the paper by nearly 500%compared to control samples having no added no starch.

Example 13 Control Unrefined Virgin Pulp

A 0.3% slurry was prepared by blending 14% by weight unrefined softwoodand hardwood pulp mixture (in the ratio of 30:70) in water.

Example 14 Control Refined Virgin Pulp

A 0.3% slurry was prepared by blending 3.5% by weight refined softwoodand hardwood pulp mixture (in the ratio of 30:70) in water.

Example 15

Handsheets were prepared using a Mark V Dynamic Paper Chemistry Jar andHand-Sheet Mold from Paper Chemistry Laboratory, Inc. (Larchmont, N.Y.).Handsheets were prepared without addition of polymers as controls, usingthe control pulps as described in Examples 14 and 15 and mixtures of thetwo. Handsheets were prepared with the addition of polymers asexperimental samples, as described below. For preparing eachexperimental handsheet, the appropriate volume of 0.3% pulp slurryprepared in accordance with Examples 13 or 14 or mixtures of the two (asapplicable) was activated with up to 2% of the selected polymer(s)(based on dry weight), as described below in more detail. Polymeradditions were performed at 5 minute intervals. This polymer-containingslurry was diluted with up to 2 L of water and added to the handsheetmaker, where it was mixed at a rate of 1100 RPM for 5 seconds, 700 RPMfor 5 seconds, and 400 RPM for 5 seconds. The water was then drainedoff. The subsequent sheet was then transferred off of the wire, pressedand dried.

Example 16 Preparation of Tethered Starch

Penford Douglas Pearl starch were dispersed in water such that thesolids content was about 20 to 25%. 1% by weight of anionicpolyacrylamide Magnafloc 919 was used as the tethering agent.

Example 17 Process for Preparing Handsheets from Activated Pulp andTethered Starch

1000 ml of a 0.3% pulp slurry prepared in accordance with Example 13 or14 or a mixture of the two (as applicable) was initially provided. Thepulp slurry was activated with 0.1% by fiber weight polyDADMAC.Separately, starch granules were prepared as a slurry HI in accordancewith Example 16. Each slurry was mixed for 5 minutes and then combinedand mixed for another 5 minutes using an overhead stirrer. Handsheetswere then produced by the method in Example 15. The final paper weightwas approximately 3 g for these handsheets.

Example 18 Caliper Analysis of Refined and Unrefined Pulp Handsheets

Handsheets prepared in Example 17 were each cut into strips and stackedto measure the caliper of 10× that of a single handsheet. The caliperswere normalized by basis weight and compared to one another in Table 3below. These results are also shown in FIG. 6.

TABLE 3 Caliper Analysis Average Sheet Caliper/ Normalized to 10xcaliper weight Weight control Condition in. g in./g inch/g * g/inchControl refined (no 0.170 4.14 0.0410 1.00 starch) Control unrefined (no0.141 2.63 0.0534 1.30 starch) Unrefined + 8% 0.151 2.76 0.0548 1.34Starch with ATA

Example 19 Tensile Strength and Bulk Enhancement with Starch GranuleAttachment

The data illustrated in FIG. 7 show the results of tensile strengthmeasurements and bulk measurements conducted on handsheet samplesprepared with a mixture of 70% unrefined and 30% refined fiber mixturewith and without starch granule addition of 8% by weight of the fibersand with and without the use of anchor-tether chemistry. The resultsdemonstrate that the ATA chemistry enhances the strength of thehandsheets made with a mixture of refined and unrefined fibers comparedto 100% unrefined fiber sheet and the one made without ATA chemistry.The strength is comparable to the sheet made with 100% refined fiberswhile showing an effective bulk increase of −10%.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. A method of increasing the bulk of a paper product formed from a pulpslurry comprising cellulose fibers, comprising: providing a firstpopulation of cellulose fibers comprising unrefined softwood fibers,forming a first slurry comprising the first population, adding anactivator polymer to the first slurry, forming complexes between theactivator polymer and the cellulose fibers, providing a secondpopulation of cellulose fibers comprising hardwood fibers, forming asecond slurry comprising the second population, preparing tether-bearingstarch granules, wherein the tether-bearing starch granules comprise atether polymer capable of interacting with the activator polymer,combining the tether-bearing starch granules with the second slurrywhereby the tether-bearing starch granules attach to the hardwoodfibers, and adding the second slurry to the first slurry to form a pulpslurry, whereby the tether-bearing starch granules attach the hardwoodfibers to the softwood fibers in the pulp slurry, thereby improving ameasure of bulk of a paper product formed from the pulp slurry.
 2. Themethod of claim 1, wherein the bulk is increased without a loss ofstrength.
 3. A method of increasing the bulk of a paper product formedfrom a pulp slurry comprising cellulose fibers, comprising: providing acellulose fiber mixture, forming a slurry comprising the cellulose fibermixture, adding an activator polymer to the slurry to form an activatedmixture comprising activated cellulose fibers, preparing tether-bearingstarch granules, wherein the tether-bearing starch granules comprise atether polymer capable of interacting with the activator polymer,combining the tether-bearing starch granules with the activated fibermixture, whereby the tether-bearing starch granules affix the activatedcellulose fibers to each other, thereby increasing the bulk of the paperproduct formed therefrom.
 4. The method of claim 3, wherein thecellulose fiber mixture comprises recycled fibers.
 5. The method ofclaim 3, wherein the cellulose fiber mixture comprises hardwood andsoftwood fibers.
 6. The method of claim 4, wherein the cellulose fibermixture comprises refined and unrefined fibers.
 7. The method of claim5, wherein the cellulose fiber mixture comprises about 40% to about 80%of hardwood fibers.
 8. The method of claim 5, wherein the cellulosefiber mixture comprises from about 60% to about 80% hardwood fibers. 9.The method of claim 5, wherein the cellulose fiber mixture comprisesfrom about 65% to about 75% hardwood fibers.
 10. A paper product formedaccording to the method of claim
 1. 11. A papermaking precursorcomprising a population of cellulose fibers in an aqueous solutionwherein: the population of cellulose fibers is dispersed in the aqueoussolution and wherein the cellulose fibers are complexed with anactivator, and wherein the aqueous solution further comprises atether-bearing particulate additive, wherein the tether-bearingparticulate additive attaches to the population of cellulose fibers byan interaction between the activator and the tether.
 12. The precursorof claim 11, wherein the additive is an organic additive.
 13. Theprecursor of claim 12, wherein the organic additive comprises a starch.14. The precursor of claim 13, wherein the starch comprises a cationicstarch.
 15. The precursor of claim 13, wherein the starch comprises ahydrophobic starch.
 16. The precursor of claim 11, wherein the additiveis an inorganic additive.
 17. A paper product formed by subjecting thepapermaking precursor of claim 11 to a papermaking process comprisingdrying.
 18. A system for papermaking, comprising: a first set ofprocessing stations, wherein a papermaking precursor is formed bycombining a population of cellulose fibers dispersed in an aqueoussolution and complexed with an activator, and a tether-bearingparticulate additive, and wherein the addition of the tether-bearingparticulate additive attaches the additive to the population ofcellulose fibers by the interaction of the activator and the tether; anda second set of processing stations.
 19. The system of claim 18, whereinthe additive is an organic additive.
 20. The system of claim 19, whereinthe organic additive comprises a starch.
 21. The system of claim 20,wherein the starch comprises a cationic starch.
 22. The system of claim20, wherein the starch comprises a hydrophobic starch.
 23. The system ofclaim 18, wherein the additive is an inorganic additive.